Bar code readers having selectable optical elements

ABSTRACT

A bar code reader for reading a symbol located at a distance from the laser comprises an array of groups of reading elements and an array of selectable liquid crystal elements. Each of the groups of reading elements have an associated predetermined operating focal distance. At least one liquid crystal element corresponds to each group of reading elements. In the bar code reader, a device activates a selected liquid crystal element to transmit light to a selected group of reading elements. In this way, the reading elements can operate at a predetermined, fixed operating focal distance.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 08/394,813filed Feb. 27, 1995, now abandoned. This application is related to U.S.patent application Ser. No. 08/111,532, filed Aug. 25, 1993, and to U.S.patent application Ser. No. 08/098,991, filed Jul. 29, 1993, which is adivisional of Ser. No. 07/864,367, filed Apr. 6, 1992, now U.S. Pat. No.5,258,605, which is a continuation of Ser. No. 07/493,134 filed Mar. 13,1990.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention generally relates to an apparatus and method operativefor electro-optically reading indicia having parts of different lightreflectivity, for example, bar code or matrix array symbols, and, moreparticularly, to devices employing a vertical cavity surface emittinglaser (VCSEL) diodes.

2. Description of the Related Art

Various optical readers and optical scanning systems have been developedheretofore for reading indicia such as bar code symbols appearing on alabel or on the surface of an article. The bar code symbol itself is acoded pattern of indicia comprised of a series of bars of various widthsspaced apart from one another to bound spaces of various widths, thebars and spaces having different light reflecting characteristics. Thereaders in scanning systems electro-optically transform the graphicindicia into electrical signals, which are decoded into alphanumericcharacters that are intended to be descriptive of the article or somecharacteristic thereof. Such characteristics are typically representedin digital form and utilized as an input to a data processing system forapplications in point-of-sale processing, inventory control and thelike. Scanning systems of this general type have been disclosed, forexample, in U.S. Pat. Nos. 4,251,798; 4,369,361; 4,387,297; 4,409,470;4,760,248; and 4,896,026, all of which have been assigned to the sameassignee as the instant application. As disclosed in some of the abovepatents, one embodiment of such a scanning system resides, inter alia,in a hand held, portable laser scanning device supported by a user,which is configured to allow the user to aim the scanning head of thedevice, and more particularly, a light beam, at a targeted symbol to beread.

The light source in a laser scanner bar code reader is typically a gaslaser or semiconductor laser. The use of semiconductor devices as thelight source is especially desirable because of their small size, lowcost and low voltage requirements. The laser beam is optically modified,typically by an optical assembly, to form a beam spot of a certain sizeat the target distance. It is preferred that the cross section of thebeam spot at the target distance be approximately the same as theminimum width between regions of different light reflectivity, i.e., thebars and spaces of the symbol. At least one bar code reader has beenproposed with two light sources to produce two light beams of differentfrequency.

One laser-based bar code scanner relevant to the present invention isdisclosed in U.S. Pat. No. 5,144,120 to Krichever et al. (and U.S.patent application Ser. No. 08/181,925, now U.S. Pat. No. 5,401,948which employs laser, optical and sensor components in conjunction with amirrorless scanner arrangement. One or more of these components aremounted on a drive for repetitive reciprocating motion either about anaxis or in a plane to effect scanning.

Another proposed bar code scanner employs electronic means for causingthe light beam to scan a bar code symbol, rather than using a mechanicaldevice. A linear array of light sources activated one at a time in aregular sequence may be imaged upon the bar code symbol to simulate ascanned beam. Instead of a single linear array of light sources, amultiple-line array may be employed, producing multiple scan lines. Sucha scanner is disclosed in U.S. Pat. No. 5,258,605 to Metlitsky et al.

Typically, the semiconductor lasers used in such bar code scanners is anedge-emitting injection laser in which the laser beam is emitted fromthe p-n junction region on a polished end face of the device.

By their physical nature, these known edge-emitting injection lasersemit a beam from a thin region at the p-n junction. Thus, for a givenpower output there is only a relatively small area from which generatedheat must be dissipated. Furthermore, a laser beam emanating from a thinsource has a large beam divergence which makes focusing difficult andresults in a wide range of variability in performance from laser tolaser.

A more recently developed form of semiconductor laser is thevertical-cavity surface-emitting laser diode (VCSEL), such as describedin "Efficient Room-Temperature Continuous-Wave AlGaInP/AlGaAs Visible(670 nm) Vertical-Cavity Surface Emitting Laser Diodes" by R. P.Schneider et al. published in IEEE Photonics Technology Letters, Vol. 6,No. 3, March 1994. Reference is also made to U.S. Pat. Nos. 5,283,447;5,285,466; 5,266,794; 5,319,496; and 5,326,386, which are herebyincorporated by reference, for background information.

The VCSEL has a substantial surface area from which the laser beam isemitted. Thus, the beam produced is less divergent in one dimension thanwith known edge-emitting type semiconductor laser diodes. The outputbeam is round, and is virtually not astigmatic. Furthermore, VCSELstypically operate at significantly lower currents than edge-emittinglaser diodes. Therefore, it also generates less heat.

In the laser beam scanning systems known in the art, a single laserlight beam is directed by a lens or other optical components along thelight path toward a target that includes a bar code symbol on thesurface. The moving-beam scanner operates by repetitively scanning thelight beam in a line or series of lines across the symbol by means ofmotion of a scanning component, such as the light source itself or amirror disposed in the path of the light beam. The scanning componentmay either sweep the beam spot across the symbol and trace a scan lineacross the pattern of the symbol, or scan the field of view of thescanner, or do both.

Bar code reading systems also include a sensor or photodetector whichdetects light reflected or scattered from the symbol. The photodetectoror sensor is positioned in the scanner in an optical path so that it hasa field of view which ensures the capture of a portion of the lightwhich is reflected or scattered off the symbol, detected, and convertedinto an electrical signal. Electronic circuitry and software decode theelectrical signal into a digital representation of the data representedby the symbol that has been scanned. For example, the analog electricalsignal generated by the photodetector is converted by a digitizer into apulse or modulated digitized signal, with the widths corresponding tothe physical widths of the bars and spaces. Such a digitized signal isthen decoded, based on the specific symbology used by the symbol, into abinary representation of the data encoded in the symbol, andsubsequently to the alpha numeric characters so represented.

The decoding process of known bar code reading system usually works inthe following way. The decoder receives the pulse width modulateddigitized signal from the digitizer, and an algorithm, implemented inthe software, attempts to decode the scan. If the start and stopcharacters and the characters between them in the scan were decodedsuccessfully and completely, the decoding process terminates and anindicator of a successful read (such as a green light and/or an audiblebeep) is provided to the user. Otherwise, the decoder receives the nextscan, performs another decode attempt on that scan, and so on, until acompletely decoded scan is achieved or no more scans are available.

Such a signal is then decoded according to the specific symbology into abinary representation of the data encoded in the symbol, and to thealphanumeric characters so represented.

Moving-beam laser scanners are not the only type of optical instrumentcapable of reading bar code symbols. Another type of bar code reader isone which incorporates detectors based on solid state imaging arrays orcharge coupled device (CCD) technology. In such prior art readers thesides of the detector are typically smaller than the symbol to be readbecause of the image reduction by the objective lens in front of thearray or CCD. The entire symbol is flooded with light from a lightsource such as lighting light emitting diodes (LED) in the scanningdevice, and each cell in the array is sequentially read out to determinethe presence of a bar or a space in the field of view of that cell.

The working range of CCD bar code scanners is rather limited as comparedto laser-based scanners and is especially low for CCD based scannerswith an LED illumination source. Other features of CCD based bar codescanners are set forth in U.S. patent application Ser. No. 08/041,281,now U.S. Pat. No. 5,396,054 which is hereby incorporated by reference,and in U.S. Pat. No. 5,210,398. These references are illustrative of thecertain technological techniques proposed for use in CCD type scannersto acquire and read indicia in which information is arranged in a twodimensional pattern.

SUMMARY OF THE INVENTION

1. Objects of the Invention

It is a general object of the invention to provide a laser scanner forbar code reading implemented on a semiconductor substrate.

It is another object of the present invention to mount light emittingand detecting elements on a miniature frame assembly capable of motionfor effecting a scanning pattern.

It is still another object of the present invention to provide an arrayof lenses and/or an array of liquid crystal shutter elements adjacent toa semiconductor substrate that includes an array of light emittingand/or detecting elements.

It is yet another object of the present invention to provide anillumination light source for a bar code reader using a vertical cavitysurface emitting laser diode.

It is still another object to enable auto alignment (i.e., do away withthe focusing step in a manufacturing process) by using VCSEL arrays toachieve multiple focus.

2. Features of the Invention

In keeping with these objects, and others which will become apparenthereinafter, one feature of this invention resides, briefly stated, inan integrated electro-optical system for reading indicia having parts ofdifferent light reflectivity, e.g. bar code symbols having alternatingbars and spaces.

In accordance with one feature of this invention, a method of readingindicia such as a bar code symbol by illuminating a field containing theindicia with a sequence of light spots by sequentially activating aplurality of separate light sources which are disposed on asemiconductor substrate; and detecting light reflected from the field toproduce an electrical signal representing light of variable intensityreflected off the indicia.

The present invention further provides a bar code reader for readingsuch indicia, including a light source component for emitting one ormore light beams; a light directing component for directing the lightbeam along a path toward the indicia; and a stationary photodetectorcomponent having a field of view and operative for detecting at least aportion of the light of variable intensity reflected off the indicia. Anoptical arrangement is provided which functions to provide a series ofindependent scans of the indicia, each scan representing a differentfocal plane disposed exteriorly to the reader.

In accordance with the teachings herein, the present invention providesa laser scanning device comprising a vertical-cavity, surface-emittinglaser, mounted on a substrate and arranged to produce a multiple laserbeam output, a scanning arrangement for effecting scanning by the laserbeam, an optical arrangement for focusing the output on a target to bescanned, and a sensor for detecting the reflected light from the target.

The surface area of a VCSEL can usefully be used to support an opticalcomponent, such as a diffractive or refractive lens, directly in frontof the diode surface. Mounting of the optical component may convenientlybe effected during fabrication to achieve desired focusing. The lasermay be operated only for short bursts in scanner applications, furtherreducing the power consumption of the VCSEL. As a result, the substratefor the VCSEL is likely to provide sufficient heat dissipation such thatfurther head sinking of the laser is not required.

In one particular form of the invention, a phased array of lasers can bearranged in groups that define focused scanning beams at differingpositions. Alternatively, scanning may be done electronically byactuating a phased array of laser diodes to create the effect of asingle scanning beam. These may be actuated selectively or in apredetermined automatic sequence. Thus, a multiline scan may beproduced, or the beam for two or more lasers may be developed to producea beam spot of a given shape on a predetermined target plane, if that isthe system requirement.

Scanning may also be effected by physically moving the laser about afield point or points. In both cases, therefore, especially in that ofthe phased array of lasers, the lower power consumption of the VCSEL isadvantageous over prior art devices.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, bestwill be understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing objects and advantages of the present invention for ascanner may be more readily understood by one skilled in the art withreference being had to the following detailed description of preferredembodiments thereof, taken in conjunction with the accompanying drawingsin which:

FIG. 1 illustrates a front plan view of a VCSEL and detector mounted ona torsional micromachined mirror;

FIG. 2 illustrates an embodiment of a bar code scanner system accordingto the invention;

FIGS. 3a-3c illustrate alternative embodiments of a bar code scannersystem according to the invention; and

FIG. 4 illustrates a hand-held bar code reader incorporating the deviceof the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings there is shown a bar code reader of thetype generally described in the above identified patents and patentapplications, the entire contents of which are all hereby incorporatedby reference herein, for reading bar code symbols, such as UPC bar codesymbols. As used in this specification and the following claims, theterm "symbol" is intended to be broadly construed and to cover not onlysymbol patterns composed of alternating bars and spaces, but also otherpatterns, as well as alphanumeric characters and, in short, any indiciahaving portions of different light reflectivity.

Referring more particularly to the first embodiment of the presentinvention, and to FIG. 1 of the drawing, there is illustrated a top planview of device structure according to the present invention including anintegrated GaAlAs VCSEL laser diode device 10 mounted on a siliconsubstrate 12, the device and substrate being collectively referred toherein as "the laser arrangement 14." The laser arrangement 14 issuspended within a miniature frame assembly 16 by a pair of TiNitorsional hinges 18 which are each secured to the substrate 12 and to arespective opposing face of the frame 16.

Electrical contacts 20, 20' pass along each hinge 18. One contact 20 isconnected to the laser diode 10, providing power from a remote source.

The active area of the VCSEL is well protected by its less sensitivesurfaces and it is possible to wafer-bond the substrate 12 with thedevice 10. The unwanted semiconductor areas (both Si and GaAlAs) canthen be etched away in order to define the center isle.

While the device of FIG. 1 is illustrated as being suspended in theframe by a torsional hinge on either side, the invention could equallybe implemented in the form of a cantilever structure as well. Theactuation mechanism for physically moving the device can beelectrostatic, bimetallic, shape memory, piezo-electric, magnetic or anyother known form by which sufficient movement can be imparted in asufficiently smooth and appropriate way. Reference may be made to U.S.patent application Ser. No. 08/141,342, filed Oct. 25, 1993, herebyincorporated by reference, to illustrate various miniaturized movableassemblies. It can also be mounted on more conventional and taut bandelements, mylar or other moving substrates. A lens can be provided ontop of the VCSEL for focusing. The lens can be diffractive optics and be"wafer bonded" to the VCSEL.

Referring now to FIG. 2, which shows the laser arrangement 14 of FIG. 1located in a housing 29 of a bar code reader 31, the laser diode 10produces a diverging light beam which is collimated by a lens array 24mounted directly on or closely adjacent to the emitting surface of thedevice. A diffuser 26 could be used in the path of the collimated beamin the embodiment in which the VCSEL is to produce uniform illumination.Diffusion may also be carried out without any collimation. If one nearsthe beam, it is preferably collimated and not diffused. If the beam isdiffused, then it is used only to illuminate the target and we need aCCD array for diffusion.

The laser light beam output, either collimated or diffused, passesthrough a window 27 in the housing 29 of the scanner apparatus 31 and isincident upon a target 28 including a bar code symbol to be read. Thelaser arrangement 14 is rotated about its torsional hinges 18 whichproduces a linear motion of the static light beam which scans the barcode symbol 28. Light reflected from the bar code is detected by aphotodetector 30, and the variation in intensity of the detected lightis then digitized and applied to a decoder of conventional arrangement.Typical movement of the laser arrangement 14 will sweep an includedangle of about 40° to perform the scan.

By using a VCSEL to illuminate the bar code target, an illuminatinglight source is realized with significantly less heat generated than inprior art devices. In this case, the beam is not scanned, but thereceiver will be either a CCD or CMOS detector array.

While the bar code reader 31 is depicted in FIG. 3 as a fixedinstallation it may, in other embodiments, take other various forms. Forexample, it could be embodied as a trigger-operated scanning gun such aswill be described in FIG. 4.

Referring back to FIG. 1, in addition to the VCSEL being integrated onthe surface of substrate 12, which acts as a "scanning mirror," theremaining portion of the mirror 12' and frame 12" can be made into aphotodetector sensor element or array. The photodetector on the mirroris of the retroreflective type, since the mirror is always turning inthe direction of the scan beam. The detectors 12" on the frame arestationary, and of the non-retroreflective type. The frame area can beincreased by filling in the empty spaces near the torsional hinges thatsupport the mirror.

Referring next to FIGS. 3a, 3b and 3c, alternative forms and embodimentsof the invention are shown. FIG. 3a illustrates the combination of alaser diode 40, which may be a VCSEL array, together with a suitablelens 41, for collimating or focusing the light emitted from the laserdiode 40, and a liquid crystal array 42. It is generally known, forexample from U.S. Pat. No. 5,071,229, to provide a variable focal lengthlens constructed of a material having the electro-optic effect such asliquid crystals, liquid crystal polymer, PLZT, etc., light blockingmeans variable in aperture size, and in general means for changing thefocal length of the variable focal length lens in synchronization withvariations of the aperture size of the light blocking means. Thus, it isknown that the brightness of visual field and the depth of fieldaccording to the focusing and the distance to the object can becontrolled with a liquid crystal device. An electromagnetic stopapparatus such as a liquid crystal stop has been proposed in the priorart to interlock the focusing adjustment of the imaging lens with thevariation of the stop diameter of the imaging lens by the combinationwith the variable focusing lens such as a liquid crystal lens. Aconventional example of the electro-optic stop apparatus is described inJapanese Publication No. Sho 59-156219.

The present invention may also utilize the LC array 42 to performscanning of the bar code symbol 43 by means of sequentially, selectivelyactivating individual elements of the LC array 42 to direct the lightemitted from the lens 41 into a predetermined pattern so as to form apath on the target symbol 43. The light reflected from the symbol willbe detected by a discrete sensor 44, as is conventional in prior art barcode reading systems. Reference here is made to U.S. Pat. No. 5,258,605hereby incorporated by reference, and in particular FIG. 20 therein.

An alternative embodiment shown in FIG. 3b utilizes a light source 47 toilluminate the bar code symbol 43. The LC array 42 is now operative inconnection with a detector array 45 which images a field of view, sothat the LC array selects and defines the portion of the field of viewwhich is imaged upon the array 45. A corresponding array 46 of focusinglens, such as the array illustrated in U.S. Pat. No. 5,345,336, may beused in connection with the array so that specific detector elements inthe array 45 are associated with a lens element of a specific opticalcharacteristic (e.g., focal length, aperture, polarization, filtering,etc.). The matching of detector elements and lens elements may be usedto more accurately image the symbol 43 on the array 45 in circumstanceswhen the symbol 43 is situated at an arbitrary or unknown distance fromthe array, or the plane of the symbol is positioned in a skewed mannerwith respect to the plane of the array.

Thus, this embodiment of the present invention provides a bar codereader for reading a symbol located at a distance from the reader,including an array of groups of reading elements, each group having anassociated predetermined operating focal distance; an array ofselectable liquid crystal elements disposed adjacent to the array ofreading elements, at least one liquid crystal element corresponding toeach group of reading elements; and means for activating a selectedliquid crystal element as so to select a corresponding group of readingelements for transmitting light through corresponding selected element,whereby the reader is operated at a predetermined selected operatingfocal distance.

In lieu of using a liquid crystal matrix, as shown in FIGS. 3a and 3b,it is also possible to use an array of miniature mirrors in its place inthe path of the outgoing or incoming light beam, such as described inthe parent application to the present application. By selectivelyactivating individual rows of such mirrors (or predetermined ones ofsuch mirrors in a sequential pattern), one can "select" either specificlight source elements (such as in a VCSEL array of light sources) ordetector elements (such as in the array 45) depending upon the type ofscanning pattern (or field of view imaging) one wishes to implement.Deformable mirror devices, (hereinafter "DMDs") such as those of TexasInstruments as described in the article "IBM, TI Announce Better Ways toManipulate Light Signals," IEEE Institute, November 1989, Vol. 13, No.11 may also be used in place of, or in addition to, the liquid crystalmatrix. See also U.S. Pat. Nos. 5,256,269, 5,083,857 and 4,441,791. Asnoted in such references, DMDs depend on the same sort of addresscircuitry as dynamic RAMs to access an array of electrodes, which lie onthe chip's surface and control the mirror pixel elements poised abovethem. DMDs also have both analog and digital capability. For an analogapplication, applying charge to one of the two address electrodesrotates a mirror pixel in that direction; increasing the voltageincreases the angle the mirror rotates. The applications envisioned hereemploy full rotation in one direction or the other.

FIG. 3c is an enlarged view of still another embodiment of the inventionsimilar to that of FIG. 3a. FIG. 3c shows a two-dimensional array 33 ofVCSEL lasers 10 arranged in rows and columns 32 and disposed in a commonsubstrate 34. An array of lenses 35 are similarly arranged in the pathof the output of the device. While the array of lenses 35 is shownremote from the VCSEL in FIG. 3c, they may also be advantageouslymounted directly on the laser beam emitting substrate as in FIG. 2.Reference may be made to U.S. Pat. No. 5,345,336 as an example of oneimplementation depicting a lens array disposed closely adjacent to asemiconductor light source. Another lens 38 is disposed in the beam pathto focus each individual beam at different distances D₁, D₂ and D₃, forexample.

In this embodiment, there is no physical movement of the device toeffect scanning, but in other embodiments an array may be located on amoving substrate. In FIG. 3, the effect of scanning is created bysequential excitation of the VCSELs 10 in the columns of the array. Bythis sequential excitation the equivalent of a single scanning beam iscreated such that a bar code 37 is swept in order for a detector 38 tobe able to pick up the variations in intensity of light reflectedtherefrom for decoding in the conventional way.

The invention may be carried out with various types of VCSEL devices,those incorporating II-VI or more especially III-V Group compoundsemiconductor materials layers are preferred.

The array of lenses 35 is, in one embodiment, arranged to provide asingle scanning beam effect with one plane of focus. However, the arrayof lenses 35 can also be designed to create a sequence of beams beingfocused at different planes. In this case the focal plane of interestcould be selected manually or be part of an automatic sequence, whichrepeats until the decoding apparatus acknowledges receipt ofsuccessfully decoded information. Thus, the present invention alsoprovides a bar code reader for reading a symbol located at a distancefrom the reader, comprising an array of groups of reading elements, eachgroup having an associated predetermined operating focal distance; anarray of selectable liquid crystal or DMD elements disposed adjacent tosaid array of reading elements, at least one liquid crystal or DMDelement corresponding to each group of reading elements; and means foractivating a selected liquid crystal or DMD element so as to select acorresponding group of reading elements for transmitting light throughcorresponding selected element whereby the reader is operated at apredetermined selected operating focal distance.

Of course, the present invention can be made to work equally well withlight emitted at wavelengths in the visible or in the infra-red range.

In a CCD reader, for example, employing an optical bandpass filterbefore the detector can reduce the ambient light reaching the detector.The combination of the filter and the high power output from the lasers(resulting in very good target illumination) can significantly increasethe working range of such detectors, which is especially important forimaging types of detectors. FIG. 4 illustrates a highly simplifiedembodiment of one type of bar code reader that may utilize theintegrated electro-optical device of the present invention. A reader 100may be implemented in a hand-held scanner, as illustrated, or a desk-topworkstation of stationary scanner. In a preferred embodiment, thearrangement is implemented in a housing 155 that includes an exit port156 through which an outgoing laser light beam 151 is directed toimpinge on, and to be scanned across, symbols 170 located exteriorly ofthe housing.

The hand-held device of FIG. 4 is generally of the style disclosed inU.S. Pat. No. 4,760,248 issued by Swartz et al., or in U.S. Pat. No.4,896,026 assigned to Symbol Technologies, Inc. and also similar to theconfiguration of a bar code reader commercially available as part numberLS 8100, LS 2000 or LS 3000 from Symbol Technologies, Inc.Alternatively, or in addition, features of U.S. Pat. No. 4,387,297issued to Swartz et al. or U.S. Pat. No. 4,409,470 issued to Shepard etal., both patents assigned to Symbol Technologies, Inc., may be employedin constructing the bar code reader unit of FIG. 5. These U.S. Pat. Nos.4,760,248, 4,896,026, and 4,409,470 are incorporated herein byreference, but the general design of such devices will briefly bedescribed here for reference.

Referring to FIG. 4 in more detail, an outgoing light beam 151 isgenerated in the reader 100, usually by an electro-optic device of thepresent invention, and directed to impinge upon a bar code symboldisposed on a target a few inches from the front of the reader unit. Theoutgoing beam 151 is scanned in a scan pattern, and the user positionsthe hand-held unit so this scan pattern traverses the symbol to be read.Reflected and/or scattered light 152 from the symbol is detected by alight-responsive device 158 in the reader unit, producing serialelectrical signals to be processed and decoded for reproducing the datarepresented by the bar code. As used hereinafter, the term "reflectedlight" shall mean reflected and/or scattered light.

In a preferred embodiment, the reader unit 100 is a gun shaped devicehaving a pistol-grip type of handle 153. A movable trigger 154 isemployed to allow the user to activate the light beam 151 and detectorcircuitry when the user has positioned the device to point at the symbolto be read. A lightweight plastic housing 155 contains the laser lightsource 146, the detector 158, the optics 157, 147, 159, and signalprocessing circuitry including a CPU 140 as well as power source orbattery 162. A light-transmissive window 156 in the front end of thehousing 155 allows the outgoing light beam 151 to exit and the incomingreflected light 152 to enter. The reader 100 is designed to be aimed ata bar code symbol spaced from the symbol, i.e., not touching the symbolor moving across the symbol. Typically, this type of hand-held bar codereader is specified to operate in the range of perhaps several inches.

The reader 100 may also function as a portable computer terminal, andinclude a keyboard 148 and a display 149, such as described in thepreviously noted U.S. Pat. No. 4,409,470.

Although the present invention has been described with respect toreading one or two dimensional bar codes, it is not limited to suchembodiments, but may also be applicable to more complex indicia scanningapplications. It is conceivable that the method of the present inventionmay also find application for use with various machine vision or opticalcharacter recognition applications in which information is derived fromother types of indicia such as characters or from the surfacecharacteristics of the article being scanned.

In all of the various embodiments, the elements of the scanner may beassembled into a very compact package that allows the entire scanner tobe fabricated as a single printed circuit board of integral module. Sucha module can interchangeably be used as the laser scanning element for avariety of different types of data acquisition systems. For example, themodule may be alternately used in a hand-held scanner, a table topscanner attached to a flexible arm or mounting extending over thesurface of the table or attached to the underside of the table top, ormounted as a subcomponent or subassembly of a more sophisticated dataacquisition system. Control or data lines associated with suchcomponents may be connected to an electrical connector mounted on theedge or external surface of the module to enable the module to beelectrically connected to a mating connector associated with otherelements of data acquisition system.

An individual module may have specific scanning or decodingcharacteristics associated with it, e.g. operability at a certainworking distance, or operability with a specific symbology or printingdensity. The characteristics may also be defined through the manualsetting of control switches associated with the module. The user mayalso adapt the data acquisition system to scan different types ofarticles or the system may be adapted for different applications byinterchanging modules on the data acquisition system through the use ofthe simple electrical connector.

The scanning module described above may also be implemented within aself-contained data acquisition system including one or more suchcomponents as keyboard, display, printer, data storage, applicationsoftware, and data bases. Such a system may also include acommunications interface to permit the data acquisition system tocommunicate with other components of a local area network or with thetelephone exchange network, either through a modem or an ISDN interface,or by low power radio broadcast from the portable terminal to astationary receiver.

It will be understood that each of the features described above, or twoor more together, may find a useful application in other types ofscanners and bar code readers differing from the types described above.

While the invention has been illustrated and described as embodied in itis not intended to be limited to the details shown, since variousmodifications and structural changes may be made without departing inany way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can readily adapt it for variousapplications without omitting features that, from the standpoint ofprior art, fairly constitute essential characteristics of the generic orspecific aspects of this invention and, therefore, such adaptationsshould and are intended to be comprehended within the meaning and rangeof equivalence of the following claims.

What is claimed is:
 1. A bar code reader for reading a bar code symbol,comprising:an array of detector elements; an array of selectable opticalelements disposed proximate to the array of detector elements, whereinthe optical elements correspond to the detector elements; an array offocusing lenses positioned between the array of selectable opticalelements and the array of detector elements; and means for selecting anoptical element to cause at least one of the corresponding detectorelements associated with the optical element to receive light reflectedfrom the bar code symbol in focus.
 2. A bar code reader for reading abar code symbol according to claim 1, wherein said means for selectingselects based upon a distance between the bar code symbol and thedetector elements.
 3. The bar code reader according to claim 1, whereinthe array of focusing lenses is attached to the array of detectorelements.
 4. The bar code reader according to claim 1, wherein theoptical elements selectively transmit light.
 5. The bar code readeraccording to claim 4, wherein the optical elements are liquid crystalelements.
 6. The bar code reader according to claim 1, wherein theoptical elements selectively reflect light.
 7. The bar code readeraccording to claim 6, wherein the optical elements are miniature mirrorelements.
 8. The bar code reader according to claim 1, wherein the meansfor selecting causes the detector elements to receive light such thatless than the entire bar code symbol is detected at one time.
 9. The barcode reader according to claim 1, wherein the means for selecting causesthe detector elements to receive light such that the entire bar codesymbol is detected at one time.
 10. The bar code reader according toclaim 1, further comprising a light source for emitting a light beamonto the bar code symbol.
 11. The bar code reader according to claim 1,wherein the array of optical elements is disposed in a fixed relationwith respect to the array of detector elements.
 12. The bar code readeraccording to claim 1, wherein the detector elements are charge coupleddevices.
 13. A bar code reader for reading a bar code symbol,comprising:an array of detector elements; an array of selectable liquidcrystal elements optically coupled to the array of detector elements,wherein the liquid crystal elements correspond to the detector elements;an array of focusing lenses disposed adjacent to the array of detectorelements, wherein each focusing lens corresponds to at least onedetector element; and means for selecting a liquid crystal element tocause at least one of the corresponding detector elements associatedwith the liquid crystal element to receive light reflected from the barcode symbol in focus.
 14. A bar code reader for reading a bar codesymbol according to claim 13, wherein said means for selecting selectsbased upon a distance between the bar code symbol and the detectorelements.
 15. The bar code reader according to claim 13, wherein thearray of focusing lenses is attached to the array of detector elements.16. The bar code reader according to claim 13, further comprising anarray of miniature mirrors disposed adjacent to the array of liquidcrystal elements.
 17. The bar code reader according to claim 13, whereinthe means for selecting causes the detector elements to receive lightsuch that less than the entire bar code symbol is detected at one time.18. The bar code reader according to claim 13, wherein the means forselecting causes the detector elements to receive light such that theentire bar code symbol is detected at one time.
 19. The bar code readeraccording to claim 13, further comprising a light source for emitting alight beam onto the bar code symbol.
 20. The bar code reader accordingto claim 13, wherein the array of liquid crystal elements is disposed ina fixed relation with respect to the array of detector elements.
 21. Thebar code reader according to claim 13, wherein the detector elements arecharge coupled devices.
 22. A bar code reader for reading a bar codesymbol, comprising:an array of detector elements; an array of selectableminiature mirror elements optically coupled to the array of detectorelements, wherein the miniature mirror elements correspond to thedetector elements; an array of focusing lenses disposed adjacent to thearray of detector elements, wherein each focusing lens corresponds to atleast one detector element; and means for selecting a miniature mirrorelement to cause at least one of the corresponding detector elementsassociated with the miniature mirror element to receive light reflectedfrom the bar code symbol in focus.
 23. A bar code reader for reading abar code symbol according to claim 22, wherein said means for selectingselects based upon a distance between the symbol and the detectorelements.
 24. The bar code reader according to claim 22, wherein thearray of focusing lenses is attached to the array of detector elements.25. The bar code reader according to claim 22, wherein the means forselecting causes the detector elements to receive light such that lessthan the entire bar code symbol is detected at one time.
 26. The barcode reader according to claim 22, wherein the means for selectingcauses the detector elements to receive light such that the entire barcode symbol is detected at one time.
 27. The bar code reader accordingto claim 22, further comprising a light source for emitting a light beamonto the bar code symbol.
 28. The bar code reader according to claim 22,wherein the detector elements are charge coupled devices.
 29. A methodof reading a bar code symbol, comprising the steps of:spacing an arrayof detector elements from an array of selectable optical elements;disposing an array of focusing lenses adjacent to the detector array,each focusing lens corresponding to at least one detector element;selectively activating the optical elements, which correspond to thedetector elements; and detecting light reflected from the bar codesymbol, via the optical elements, at the corresponding detectorelements, wherein the detected light is in focus.
 30. The method ofreading a bar code symbol according to claim 29, further comprisingattaching the array of focusing lenses to the detector array.
 31. Themethod according to claim 29, further comprising the step of emitting alight beam onto the bar code symbol.
 32. The method according to claim29, wherein the step of selectively activating the optical elementscomprises the substep of selectively activating the optical elements todetect at one time less than the entire bar code symbol.
 33. The methodaccording to claim 29, wherein the step of selectively activating theoptical elements comprises the substep of selectively activating theoptical elements to detect at one time the entire bar code symbol. 34.The method according to claim 29, wherein the step of selectivelyactivating the optical elements comprises the substep of selectivelyactivating the optical elements such that the bar code symbol is read ata selected focal distance.